They get a full ride scholarship in exchange for their bodies and being practice subjects for the biochemistry club. For a lot of students, also getting a free cyborg body out of it is a perk rather than another cost. It's only because Yuka didn't pay attention signing up for it that she's surprised by it. Her body shouldn't age without getting it remodeled since she's a robot, but I think she's would be graduating as normal shortly after the last page.
They probably should've had a page explaining the whole program at once somewhere instead of breaking up the exposition across several pages of robot girls in distress.